diff options
| -rw-r--r-- | drivers/char/agp/generic.c | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/drivers/char/agp/generic.c b/drivers/char/agp/generic.c index c3920016168..ca4629f66d1 100644 --- a/drivers/char/agp/generic.c +++ b/drivers/char/agp/generic.c @@ -419,6 +419,31 @@ static void agp_v2_parse_one(u32 *requested_mode, u32 *bridge_agpstat, u32 *vga_ *requested_mode &= ~AGP2_RESERVED_MASK; } + /* + * Some dumb bridges are programmed to disobey the AGP2 spec. + * This is likely a BIOS misprogramming rather than poweron default, or + * it would be a lot more common. + * https://bugs.freedesktop.org/show_bug.cgi?id=8816 + * AGPv2 spec 6.1.9 states: + * The RATE field indicates the data transfer rates supported by this + * device. A.G.P. devices must report all that apply. + * Fix them up as best we can. + */ + switch (*bridge_agpstat & 7) { + case 4: + *bridge_agpstat |= (AGPSTAT2_2X | AGPSTAT2_1X); + printk(KERN_INFO PFX "BIOS bug. AGP bridge claims to only support x4 rate" + "Fixing up support for x2 & x1\n"); + break; + case 2: + *bridge_agpstat |= AGPSTAT2_1X; + printk(KERN_INFO PFX "BIOS bug. AGP bridge claims to only support x2 rate" + "Fixing up support for x1\n"); + break; + default: + break; + } + /* Check the speed bits make sense. Only one should be set. */ tmp = *requested_mode & 7; switch (tmp) { |